Best animal to kill pond snails?

I have a 5 gallon tank with a betta and got some small snails, i assume they are bladder snails with some duckweed i purchased (I was not told about them). My betta has only eaten a couple, maybe 3 or 4, and at this point i have at least 30 or 40, maybe more since i saw eggs on the side. It was fine when there were just a couple and they are cute, but they poop all over and i only want a couple. Is there anything i can put in this tank that will kill a couple but not all of them or at least get rid of some of their waste? My betta is aggressive to an extent but probably wont kill something like a large snail. Its only a 5 gallon so i know my options are limited but any recommendations are appreciated. I added some pics of the snails and my tank. Sorry for the glare.

You are better off manually removing them. Put a piece of blanched vegetable in the tank for about an hour. The snails will be crawling on it. Throw it away. Repeat as needed. Remove snail eggs from glass,nplants and decoration. The excess of snails seems to indicate you are overfeeding the betta.

Overfeeding and lack of maintenance (algae and dead plants) will contribute to the snail population. I have a similar problem in my 50gallon. I purchased a couple of assassin snails but they are making a slow work of it. Assassin snails are the only animal that could go with a betta in a 5 gallon